Some thermoplastic resin compositions such as flame-retardant ABS and flame-retardant PC/ABS, or reinforced thermoplastic resin compositions made by reinforcing such thermoplastic resin compositions with fibers, are used as raw materials of a housing of electronic equipment such as a laptop personal computer and a portable device. Usually, these resin compositions are molded into a housing by means of injection molding, which is highly flexible about the shape of molded articles.
In recent years, a demand for electronic equipment to be thinner and more lightweight is getting stricter, and also a demand to be endurable against impacts and loadings while sitting inside a bag or such a container is being raised. In order to satisfy these demands, the resin used for a housing has to have not only high rigidity and impact resistance, but also high drop impact resistance.
By the way, it is known that the drop impact resistance is highly correlated with the surface impact strength measured by a falling ball test, but not so much correlated with the Izod impact strength or the Charpy impact strength. For this reason, improvements in the Izod impact strength and the Charpy impact strength may not lead to an improvement in the drop impact resistance.
Among conventionally employed housing materials for electronic equipment, non-reinforced flame-retardant ABS resins and flame-retardant PC/ABS resins have low rigidity and thus are not able to meet the recent demand of thickness reduction. In addition, glass fiber-reinforced resin compositions are not sufficient in the balance between the rigidity and the weight. For this reason, carbon fiber-reinforced thermoplastic resin compositions are now being reviewed as housing materials for electronic equipment.
However, conventional carbon fiber-reinforced thermoplastic resin compositions are brittle and involve an easy-to-break drawback for use as a housing material, although they are able to achieve high rigidity and lighter weight. As a means for overcoming this drawback, there is proposed a method in which a carboxyl group-containing olefin-based wax, or the like, is mixed in a carbon fiber-reinforced polycarbonate resin (Patent Document 1). This method described in Patent Document 1, however, involves a drawback in that the impact resistance can be improved whereas other mechanical strengths are impaired.
Moreover, in order to improve the mechanical strengths, there are proposed a method in which a silane coupling agent and an epoxy compound are used as a fiber shrinking agent for a fiber-reinforced resin composition (Patent Document 2), and a method in which an epoxy resin is added afterward (Patent Document 3). However, these methods described in Patent Documents 2 and 3 did not improve the impact resistance.
In addition, in order to improve the flame retardancy and the mechanical strengths, there are many proposals to add an epoxy compound; however, there is no proposal about a reinforced thermoplastic resin composition having improved drop impact resistance while maintaining the mechanical strengths.
Furthermore, housings of electronic equipment need to have an electromagnetic interference shielding ability (hereunder, referred to as “EMI shielding ability”). Regarding a method for providing the EMI shielding ability, usually, there are enumerated: a method in which a resin containing 10 to 20% by mass or more of a carbon fiber is used; a method in which a metallic foil or a metallic plate is inserted during the inmolding or product assembling process; a method in which a nonelectrolytic plating or a conductive coating is applied; and a method in which a magnesium alloy is used as a housing material. Of these, the method in which a magnesium alloy is used as a housing material is taking over the mainstream.
In addition, magnesium alloys are advantageous as they can achieve higher rigidity, higher strength, and lighter weight. However, magnesium alloys require time and labor for secondary processing, as well as involving a problem in that the flexibility about the shape is so limited that they are only applicable to simple shapes.    Patent Document 1: Japanese Laid-Open Patent Application No. 2001-240738    Patent Document 2: Japanese Unexamined Patent Application, First Publication No. H06-49344    Patent Document 3: Japanese Laid-Open Patent Application No. 2006-63110